In particular, the invention relates to a kitchen scale comprising a carrying plate, an in particular shell-type substructure which supports the carrying plate, weighing cells, which are interconnected between the force flow from the carrying plate to the substructure and have at least one strain gauge, which is deformed by the deformation of the weighing cell as a result of a load resting on the carrying plate, an electronics unit, which is capable of computing the weight of the load from the degree of the deformation of the weighing cells, and a display device for displaying the ascertained weight and a battery compartment for accommodating a voltage source which supplies the electronics unit with power, wherein the kitchen scale is designed as an open kitchen scale having a gap between the carrying plate and the substructure, so that water and/or moisture can penetrate through the gap into the kitchen scale and can exit from the kitchen scale, and the electronics unit and also the display device are encapsulated so as to be watertight, the carrying plate and the substructure, with the exception of the battery compartment and the encapsulated electronics unit, do not have cavities, and the battery compartment is sealed against penetrating water.
The typical kitchen scales have supporting feet below the carrying plate, via which they stand on an underlying surface. Weighing cells are then provided in the region of the connection of the supporting feet or in the supporting feet themselves. These weighing cells are deformable strain gauges, wherein the electronics unit is capable of determining the weight resting on the carrying plate via the deformation, in particular using a measurement bridge.
Another embodiment of a kitchen scale has a rather shell-like or flat substructure, wherein the weighing cells are arranged between the carrying plate and the substructure. A gap exists here between the substructure and the carrying plate, which is compressed because of the deflection of the carrying plate. The electronics unit is typically arranged in this case on the substructure, but can also be provided on the carrying plate. This also applies to the display device.
These kitchen scales have the disadvantage that they are not liquid-tight. Liquid typically cannot enter the scale during normal use in a kitchen, but the scale cannot be cleaned under running water or even in a dishwasher.
Experiments have therefore been made in designing a kitchen scale so as to be completely closed, so that it is watertight, as is known, for example, of electrical toothbrushes. Because the weighing cells have to be deflected in relation to the remaining regions of the kitchen scale due to relative movement of the carrying plate, however, a housing closed all around can only be implemented with difficulty. In particular in the region of the weighing cells, however, moisture interferes and corrupts the measurement result. This is an obstacle in particular in the field of the kitchen scales, since they typically have to have an accuracy of, for example, 1 g.
In addition, it has been shown that in spite of all efforts, a complete moisture tightness can hardly be implemented.
Kitchen scales of the type mentioned at the outset are known from DE 10 2011 051 612 A1. These kitchen scales have supporting feet below the carrying plate, via which they stand on an underlying surface. Weighing cells are then provided in the region of the connection of the supporting feet or in the supporting feet themselves. These weighing cells have strain gauges which are deformable together with the deformation of the weighing cells, wherein the electronics unit is capable of determining the weight resting on the carrying plate via the deformation of the strain gauges.
The kitchen scale has a shell-type or flat substructure, wherein the weighing cells are arranged between the carrying plate and the substructure. A gap exists here between the substructure and the carrying plate, which can be compressed, but not closed, as a result of the deflection of the carrying plate. The electronics unit is arranged in this case on the substructure, but can also be provided on the carrying plate. This also applies to the display device.
These dishwasher-suitable kitchen scales have the disadvantage that they are not liquid-tight and therefore rinsing water and contaminants or foreign bodies can penetrate into the interior of the kitchen scale. The electronics unit and the battery compartment are protected against moisture, but the weighing cells can become wet in the region of the strain gauges and can be damaged by chemical influences of the detergent or by mechanical impacts of the foreign bodies. Finally, even an increased ambient humidity, and certainly water wetting, considerably interferes with the measurement.
A weighing cell, inter alia, for weighing purposes is known from US 2005/0155435 A1, which has protection from water, in particular formed by a polymer coating, in the region of the strain gauges. This coating is watertight and comparatively costly, so that this expenditure is only worthwhile in conjunction with costly industrial scales. Household scales are under a high cost pressure, however, so that such a watertight coating is not possible here. Furthermore, the coating cannot influence the measurement accuracy.